Method of refinishing brakedrums



March 15, 1955 P. J. PARKER METHOD oF REFINISHING BRAKEDRUMS Filed Oct. 16. 1950 FIG.

INVENTo'R.

PHILLIP J. PARKER /dA/l( 'ATToRN United States Patent O METHOD F REFINISHING BRAKEDRUMS Phillip J. Parker, Cincinnati, Ohio, assignor to Barrett Equipment Co., St. Louis, Mo., a corporation of Missouri Application October 16, 1950, Serial No. 190,261

3 claims. (Cl. 29-1s2.2)

d 'Ihis invention relates to a method of refinishing brakerums.

An object of the invention is to teach a method of refinishing brakedrum surfaces whereby they will be characterized by their hardness and extreme smoothness.

Another object of the invention is to teach a method of reconditioning brakedrums whereby to impart to the braking surface a inish equal to or superior to their original finish.

Another object of the invention is to teach a method of improving the finish of the braking surface of a brakedrum by simultaneously rening the grain structure and hardening said surface.

A further object of the invention is to provide a method of improving the braking surface of a brakedrum by means of a burnishing operation performed on the braking surface while said surface s rotated at substantially the same speed at which said surface was initially trued.

These and other objects are attained by the means described herein and as disclosed in the accompanying drawings, in which Fig. 1 is a side elevational view of a turret type tool holder embodying the teachings of the present invention.

Fig. 2 is a side elevational view of the turret tool holder of Fig. l provided with finish cut and burnishing tools illustrating the relationship of the parts incident to the making of a nish-trueing cut.

Fig. 3 is a view similar to Fig. 2 but wherein the burnishing tool has been moved into operative relationship with the brakedrum surface.

Fig. 4 is a bottom end view of the turret-head, per se.

Fig. 5 is a side elevational view of the turret-head of Fig. 4 taken from the right side thereof.

The present invention is primarily directed to the method of and means for improving the finish of the braking surface of brakedrums whereby the operating characteristics and braking efficiency of a relinished brakedrum will compare favorably with the operating characteristics and braking eiiiciency of the drum when new.

It will be noted that heretofore, prior to my invention, it was not uncommon for from 16% to 30% of a new lining to be consumed in polishing the braking surface of brakedrums resurfaced in accordance with the refinishing methods presently in widespread commercial use.

The smoothness of finish is of extreme importance and cannot be too strongly emphasized since it determines not only the overall efficiency of the braking system, but determines the useful life of the brake linings.

Tests have conclusively proven that using the method and apparatus of the present invention, it is now possible to commercially reiinish a brakedrum whereby to provide such a smooth finish that not more than 8% of the new lining will be consumed during the so-called break-in period. My invention enables an operator to provide the brakedrum with a surface comparable to that of a new car drum that has been in use for about 6000 miles, having been polished to the highest possible degree and with the rate of lining wear reduced to an absolute minimum.

With reference now to Fig. l, the numeral 10 denotes generally a brakedrum, numeral 12 denoting the braking surface which the brake-lining contacts, and which surface the method and apparatus of the present invention is concerned with.

In reconditioning brakedrums, it is customary to mount them to the chuck of a lathe or similar turning device ICS for rotation about its axis of rotation. The worn surface 12 to be refinished may then be subjected to the successive cutting operations of a roughing tool 14 and a finishing tool 16 suitably secured to and carried by turret-head 18 which is secured to and carried by the forward inclined face 20 of shank 22, shank 22 being suitably secured to and carried by a slide rest, not illustrated, or the like, by which the tool is held and traversed.

With particular reference now to Fig. 4, it will be noted that turret-head 18 is provided with a pair of substantially parallel, laterally spaced tool receptive bores 24 and 26, Whose respective axes are parallel with and spaced on opposite sides of diametric center line 28-28 through the head. Plugs 30 and 32 threadably engage bores 24 and 26, respectively.

A tool such as, by way of example, a burnishing tool 34 having a hardened ball tip 36 is dimensioned to be slidably received within bore 24. Similarly, a cutting tool 38 is provided and dimensioned to be slidably received within bore 26.

Axial movement of tools 34 and 38 is accomplished by means of plugs 30 and 32, respectively, it being observed that these plugs abuttingly engage the rear ends of their respective tools.

In the preferred embodiment of the invention head 18 is likewise provided with a pair of internally threaded set screw receptive openings 40 and 42, whose respective axes are at substantial right angles with and intersect the axes of one of the bores, that is, opening 40 intersects bore 24 and the axis of opening 42 intersects the axis of bore 26.

Set screws 44 and 46 threadably engage their respective internally threaded openings whereby the forward ends of said set screws are engageable with the side walls of the tools mounted in bores 24 and 26 for securing said tools against turning movement about their longitudinal axes.

As best illustrated in Figs. l, 4 and 5, head 18 includes a front face 50 and a rear face 52. A stub shaft 54 is formed integrally with the head and projects axially from rear face 52, said stub shaft being rotatably receivable within a complementary recessed portion 56 provided in inclined bearing surface 20 of shank 22. The stub shaft may be securely though releasably fastened relative to the shank by means of a fastening member 58 having a threaded portion 60 dimensioned to engage internally threaded portion 60 of the stub shaft 54.

Suitable indexing means are provided for indexing the tool holder in one or the other of two normal positions with respect to said shank. Said indexing means may comprise a pair of laterally spaced, axially aligned notches or depressions 70 provided in rear face 52 of head 18.

A latching member 74 slidably engages a channelway 75 provided in shank 22, said member being normally urged forwardly by means of a spring 72 for thereby yieldingly disposing its forward end in abutting relationship with rear face S2 of the head or in seating engagement with one or the other of depressions 70.

Loosening of fastening member 58 will permit head 18 to be rotated relative to shank 22 for selectively disposing one or the other of the tools in operative position which will be automatically established incident to engagement of latching member 74 with one or the other of notches 70. Tightening of fastening element 58 will positively, though releasably lock turret-head 18 relative to shank 22 against accidental or unintentional movement relative thereto.

With particular reference to Figs. 2 and 3, it will be noted that after surface 12 of the drum has been initially trued and smoothed by cutting tools 14 and 16, the surface is then subjected to the action of finishing tool 80 which, in the preferred embodiment of the invention, is a cutting tool which will take a fine cut and therefore remove but a small amount of material from surface 12. After surface 12 has thus been trued and smoothed by means of cutting tool 80, the interior of the drum should be carefully cleansed of all chips and other foreign particles, after which it is thoroughly lubricated with a lubricant having such characteristics as to provide a lubrieating film which will remain effective when subjected to the burnishing operation hereinafter described.

Solely by way of example and not by way of limitation, I have found that an excellent lubricant for the burnishing operation may be made up by thoroughly mixing together three quarts of SAE 90 hypoid lubricant with one pint of a so-called super-lubricant such as the product sold by the Bardahl Oil Co. of St. Louis, Missouri, under the trade-mark Bardahl, or Luboid of the Luboid Company of Milwaukee, Wisconsin. The characteristics of these and other commercially available super-lubricants is to increase many-fold the pressures under which ordinary lubricants may be subjected to by providing an extremely tough film which protects and lubricates under conditions where the same lubricants without benefit of the super-lubricants would be squeezed out by the pressures applied thereto.

I then add 6 ounces of powdered or colloidal graphite and 6 ounces of powdered mica. The resultant mixture is thoroughly agitated and then applied liberally to surface 12.

I do not profess to know the exact function of the graphite and mica although both ingredients are required for best results. By using a burnishing lubricant having the composition hereinabove set forth I am able to increase the pressure on the burnishing tool by at least 300% over the pressures obtainable with an ordinary lubricant before scoring of surface 12 will occur.

In performing the actual burnishing operation the burnishing tool 36 is first brought into contacting relationship with the trued surface 12 of the drum and then advanced forwardly, that is, into surface 12, by an amount not exceeding .O03 inch while the drum is being rotated at substantially the same speed at which it was rotated during the cutting and trueing operation of tool 80. The transverse feed of the lathe should then be immediately engaged for very slowly but continuously withdrawing j he burnishing tool outwardly across surface 12 of the rum.

It has been conclusively established that one pass of the hardened ball burnishing tool across surface 12 of the drum subjected to the pressure resulting from introducing the ball by not more than .003 inch into surface 12 in the presence of a suitable lubricant will simultaneously improve the grain structure and increase the superficial hardness of surface 12 from 20% to 25%.

By thus improving the hardness and smoothness of the refnished surface of the drum, the break-in period heretofore encountered on refinished drums has been substantially eliminated and the brake-shoes may be adjusted in accordance with the manufacturers original specification.

From the foregoing it will be noted that I am thus able to perform the various cutting, trueing and burnishing operations while rotating the drum at one speed thereby eliminating the time-consuming operations heretofore required for changing the rotational speed of the drums incident to the various cutting and trueing operations.

It should likewise be noted that I have provided simple yet positive acting, easily accessible means for adjusting the setting of the tools relative to turret-head 18.

What is claimed is:

1. The method of improving the finishi of the braking surface of a brake drum, which method comprises the steps of rotating said drum about its axis of rotation, of truing and smoothing the braking surface by means of a finish cut operation, and of then further refining the grain of and hardening said surface by subjecting it to the burnishing action of a hardened ball tool in the presence of a lubricant the film of which will withstand the pressures developed incident to the burnishing operation, wherein the magnitude of the burnishing pressure is that which results from forcing said ball tool into the surface of the rotating drum to approximately .003 inch.

2. The method of improving the finish of the braking surface of a brake drum, which method comprises the steps of rotating said drum about its axis of rotation, of trueing and smoothing the braking surface by means of a finish cut, of cleansing the surface of all loose foreign material, of coating said surface with a lubricant approximating six parts of SAE hypoid lubricant, one part superlubricant, six ounces of powdered graphite and six ounces of powdered mica, and of then subjecting said lubricated surface to the burnishing action of a hardened ball tool forced against and into said surface to approximately .003 inch while rotating the drum at substantially the same rotational speed as during the finish cut.

3. The method of improving the finish of the braking surface of a brake drum, which method comprises the steps of rotating said drum about its axis of rotation, of trueing and smoothing the braking surface by means of a finish cut, of cleansing the surface of all loose foreign material, of coating said surface with a lubricant approximating six parts of SAE 90 hypoid lubricant, one part superlubricant, six ounces of colloidal graphite and six ounces of powdered mica, and of then subjecting said lubricated surface to the burnishing action of a hardened ball tool forced against and into said surface to approximately .003 inch while rotating the drum at substantially the same rotational speed as during the finish cut.

References Cited in the file of this patent UNITED STATES PATENTS 1,010,127 Dingley Nov. 28, 1911 1,227,486 Newman et al. May 22, 1917 1,592,938 Johansson July 20, 1926 1,683,044 Mongeau Sept. 4, 1928 1,811,999 Evans June 30, 1931 1,949,527 Briney Mar. 6, 1934 1,998,048 Farr Apr. 16, 1935 2,162,072 Eksergian June 13, 1939 2,181,835 Place Nov. 28, 1939 2,344,509 Guenther Mar. 21, 1944 2,354,218 Murray July 25, 1944 2,378,843 Haberstump June 19, 1945 2,378,871 Stephens June 19, 1945 OTHER REFERENCES Page 718, Lubricating Greases, by Klemgard; Reinhold Publishing Co., New York, New York. 

